Cathode ray tube



Aug. 20, 1957 Filed Jan. 27, l955 K. HOAGLAND 2,803,768

CATHODE RAY TUBE 3 Sheets-Sheet l INVEN TOR. KENNETH A. HOA'GLAND Aug. 20, 1957 K. HOAGLAND CATHODE RAY TUBE 3 Sheets-Sheet :2

Filed Jan. 27, 1955 INVENTOR. KENNETH A. HOAGLAND BY f "' ORNEYS Aug. 20, 1957 K. HOAGLAND 2,803,768

CATHODE RAY TUBE Filed Jan. 27, 1955 5 Sheets-Sheet 3 FOCUS ELECTRODE 38 SUPPLY sffiL 32/ SOURCE GREEN SIGNAL 34 SOURCE CONVERGENCE ELECTROD 36 SUPPLY H.V. ANODE SUPPLY Fig.5

INVENTOR.

KENNETH A. HOAGLAND J Aj R E-Ys United States Patent Office 2,803,768 Patented Aug. 20, 1957 2,803,768 CATHODE RAY TUBE Kenneth Hoagland, Nutley, N. .J., assignor to Allen B.

Du Mont Laboratories, Inc., Clifton, N. J., a corporation of Delaware Application January 27, 1955, Serial No. 484,333 12 Claims. (Cl. 313-70) This invention relates to multi-gun cathode ray tubes for color television and particularly to the focusing and convergence structure of such tubes.

It has been the practice heretofore in color television cathode ray tubes to have a convergence electrode which is common to all of the electron guns in the tube and to form an electron lens between the end of this convergence electrode and an anode wall coating on the inner neck of the tube. The electron guns (usually three) are constructed with anodes which cooperate with the convergence electrode to form an electron lens for each gun. An example of such a tube and a description of the electron lenses formed is given in a copendingapplication entitled Cathode Ray Tube, filed by Emil Sanford on November 4, 1954, Serial No. 466,713.

In tubes of the type described, the anode voltage is usually in the region of 20,000 volts or thereabouts. In order to form an electron lens it is necessary to have a difference of potential between electrodes and accordingly the convergence electrode must be operated at a higher or lower potential than the anode. For practical reasons, a lower potential usually is chosen and the convergence electrode therefore may operate at a voltage less than 10,000 volts. This requirement for a difference of potential makes it necessary to operate the anode portions of the three individual or separate electron guns at still lower voltages, for instance, about 3,000 volts.

In order to keep the electron beams from the guns converged at or near the screen of the tube, it is necessary to apply a varying convergence voltage to the convergence electrode. Not only does this varying voltage affect the strength of the convergence electron lens between the convergence electrode and the anode, but it also affects the strength of the separate beam focusing lenses. Furthermore, the separate electron guns are required to form electron beams in a relatively low voltage environment, the voltage available to each gun being the 10,000 volt potential of the convergence lens, and the current absorbed by the convergence electrode is relatively large,

which raises a problem of regulation of the convergence electrode supply voltage. I I

It is one object of this invention to provide an improved multi-gun cathode ray tube having simplified convergence and focus structure.

Other objects are to provide a multi-gun cathode ray tube having separate electron beam focusing structures and convergence structures which are isolated so that a variation of convergence voltage does. not affect the focus of the separate electron beams, to provide an improved focusing and convergence structure which allows high voltage operation of the separate electron guns, and to provide a converging and focusing structure which requires little or no current.

Further objects will be apparent after reading the following specification, together with the drawing in which;

Figure 1 is a fragmentary perspective view of a cathode ray tube embodying the principles of this invention, the tube envelope being broken away to show the interior construction;

Figure 2 is a similar view of a different embodiment of the electrode structure in Figure 1;

Figure 3 is a similar view of another modification of the electrode structure of Figure 1;

Figure 4 is a similar view of a modification of the electrode structure of Figure 3; and

Figure 5 is a diagrammatical sketch showing the electrical supply sources connected to the tube of Figure l.

The invention comprises the combination of a multiple electron beam source, a convergence electrode, and an anode. The source includes an electrode structure to generate and focus a plurality of electron beams, usually three in number, and the electrode structure comprises an anode, generally referred to as a second anode, to

which the anode first mentioned is directly connected The second anode operates on the electron beams in two ways; on one side the second anode is the last electrode to act on and assist in the focus of the beams individually, and on the other side the second anode cooperates with the convergence electrode and the first-named anode to form an einzel lens structure which operates simultaneously on all of the electron beams to converge them on a confined area of the target area, or fluorescent screen of the cathode ray tube.

The multiple electron beam source may [be made up of a plurality of separate electron guns mechanically and perhaps electrically connected together, or the source may be made up of a unitary structure having individual passageways for the electron beams. In either case, the source comprises a cathode, control grid, second grid, first anode, and the aforementioned second anode. Most of these electrodes, with certain exceptions, may be either unitary with separate passageways orentirely individual electrodes. One exception is that there must be either a separate cathode or control grid, or both, to control the intensity of each beam individually. Another exception is that a separate second grid for each electron beam, While not absolutely necessary, makes it easier to control the electrical characteristics of the tube by providing means to adjust for production tolerances. V

In the multiple beam source just described a potential is applied between the first the individual electron beams. As an alternative, the

first and second anodes may be electrically connected together and a focusing electrode inserted therebetween to form an individual einzel lens for each electron beam.

In Figure 1, only a portion of the neck 11 of a cathode .ray tube is shown. Located Within the neck 11 is a mul tiple electron beam source comprising three electron beam forming guns. Because of the fact that the electron beam from one of these guns is commonly directed to impinge on fluorescent all of the components of that gun will be designated by the addition of the letter r to the reference characters. Similarly, the letters b and g will identify parts of the other two guns respectively. Eachelectron gun comprises a contr-ol grid 12 which includes within it a cathode not visible in this drawing. The three control grids 12r, 12b and 12g are arranged in an equilateral triangular relationship and supported by a plurality of insulating rods which appear in the present figure. Three corresponding second grids 141', 14b and 14g are also supported by the rods 13 in predetermined spaced relationship to the grids 12r, 12b and 12g. Similarly, three anodes 16r, 16b and 16g, called first anodes, three focus electrodes 17r, 17band 17g, and three field denfiing electrodes, or second 13, not all of anodes, 18r, 18b and 18g are also supported. by the rods;

13. The cathodes, which are not shown, the anodes 16,; the second grids 14, and the control grids 12, form prefocusing structures for each of the electron guns.

All three of the anodes 18r, 18b and 18g, are connected mechanically and electrically to a common end plate 19 which may, if desired be provided with a cylindrical rim.

and second anodes to focus elements (not shown) which emit red light,

21 convergence electrode in the form of a metallic cylinder22 is located beyond the plate 19. Conductive anode wall coating 23 is placed on the internal surface of the neck 11 and connection thereto is made by an anode contact button 24 or any other convenient means.

The anodes 16x, 16b and 16g preferably are also electrically connected together and are connected to the anodes 18r, 18b and by means of a wire 26. Thus, the anodes 16 and 18 form the two outer electrodes of a separate einzel lens for focusing each of the electron guns and the electrodes 17 form the center electrodes therefor. In addition, the anodes 18 are electrically connected as, for instance, by one or more spring contact members 27 to the wall coating 23 which may be termed an additional anode so that the anodes 18 or,'as it may be considered, the plate 19 form one outer electrode and the anode 23 forms the other outer electrode of an einzel lens of which the convergence electrode 22 forms the center electrode. Since the power of the focusing lenses is controlled by the electrodes '17 and the convergence lens is separately con trolled by electrode 22, varying the power of the focusing lenses has little or no efiect on the power of the convergenc e lens, and vice versa.

Figure 2 shows a modification of the electron beam source shown in Figure l, the principal difference being that individual focusing of the three electron beams is accomplished in the structure of Figure 2, by means of a difference of potential applied between the first anodes 116 and the second anodes 118. The lens, so formed, is known as a two cylinder lens and the anodes 116 are operated at a voltage considerably below the voltage of anodes 118. However, since anodes 118 are electrically connected to the wall coating, as in the case of anodes 18 in Figure 1, the total voltage of each electron gun in Figure 2 is the same as in Figure 1. In order to focus the electron beams of the structure in Figure 2 on the fluorescent screen (not shown) a variable voltage may be supplied to anodes 116 Figure 3 shows a modification in which a unitary electrode structure, rather than the separate electron struc ture. of Figures. 1 and 2, is used to generate the three electron. beams. In Figure 3, the large diameter cylinder 112 at one end of the electrode structure is a control grid which encloses three cathodes of the type normally used in cathode, ray tubes. Control grid 112 is provided with a plate closing one end of the tubular portion except for three apertures located directly in front of the electron emitting portions of the cathodes. Only oneof these apertures. 27g is shown in the drawing. The electrode structure also includes a second grid electrode, as did the structures shown in Figures 1 and 2. However, thesecond grid structure in Figure 3. comprises a single insulating plate 28. on which threewedge-shaped conductive segments 1141', 114b and 114g are deposited. Each of these wedgeshaped sections is provided with an aperture through which the electron beam passes. The second grid structure is not limited to a plurality of wedge-shaped metal segments on an insulating plate but may be of the type shown in Figures 1 and 2, i. e. a plurality of short tubular electrodes closed at one end except for a central aperture. The second grid segments 114 may even be connected together if spacing tolerances are maintained with sufiicient pre cision, but, particularly when the tube is to be made by mass production techniques, it may be desirable that the second grid electrodes be separatefor each electron beam.

The individual beam-focusing structure of Figure 3 employs the two electrode arrangement used in Figure 2, but in the case of Figure 3 the first anode 216 is a large diameter cylinder provided with a closure plat-e (not shown) at the end closer to the control grid 112. The closure plate is provided with three apertures which are aligned with the apertures in the control grid 112 and the second grid- 114. Anode 216 is also provided with a clo sure 29 which is likewise pierced by three apertures to form separate passageways for each of *the three electron beams. Only aperture 30g of these three apertures an pears in the drawing. The second anode 218 is a large diameter cylinder of the same diameter as anode 216 although the equality of diameter is a matter of mechanical preference and not an electrical requirement. Anode 218 is also provided with a three-aperture closure member (not shown) facing the closure member 29 of anode 216. The reason for these two closure members on proximal ends on anodes 216 and 218 is to provide individual focusing of the three electron beams. Without some separation of the electron beam paths through separate passageways, a difference of potential applied between anodes 216 and 218 would serve to converge the electron beam toward a single point on the screen (not shown) of the tube, and would be directly opposed to the object of separating the func tions of focus and convergence.

Convergence of the three beams is provided for by an electron lens comprising anode 218, a convergence electrode 22 and an additional anode 31 which, in this instance, is a separate metallic ring supported by the electrode structure and having a reduced diameter end which extends inside the convergence electrode cylinder 22 but is insulated therefrom. In the normal case, the tube of Figure 3 will also be provided with a wall coating 23 electrically connected to the additional anode 31 and to the second anode 218. The electron convergence lens formed by these latter elements is an einzel lens of the same type as described in connection with Figures 1 and 2, with electrode 22 being the inner electrode and anodes 218 and 31 being the two outer electrodes.

Figure 4 shows a modification of the structure shown in Figure 3. The structure in Figure 4 includes a separate focus electrode 117 inserted between first anode 316 and second anode 318'. In this arrangement, anodes 316 and 318 are connected together to form with focus electrode 117 an einzel lens for each electron beam. Preferably, the proximal ends of anodes 316 and 318 are provided with aperture closure members as in Figure 3 to provide separate passageways for the electron beams and the focus electrode 117 may be a conductive plate having a proper thickness to effect the desired focusing of the electron beams.

It will be understood of course that various combinations of the features of Figures l4 may be made as is well known to those, skilled in the art. For example, the unitary first and second anodes of Figures 3 and 4 could be utilized with separate control grids and second grids of the type shown in Figures 1 and 2. Numerous other permutations of the elements will occur to those skilled in e an,

Figure 5 is a. schematic drawing of two electron guns in the beam forming structure of the tube shown in Figure 1. Figure 5 also shows power supply connections to the various electrodes. A signal source 32 labeled Red Signal Source is connected to the grid 12r and the cathode 33!? of one electron gun and a signal source 34 labeled Green Signal Source" is connected to the grid 12g and'the cathode 33g of the other electron gun. The terms red and green are used to signify that these signal sources supply to the respective grids and cathode electrical signal information corresponding to red and green portions of television images to be reproduced by the tube. A convergence electrode supply 36 is connected to the convergence electrode 22 and a high voltage anode supply 37 is connected to the wall coating 23 and, by means of a connection 127, to the first anodes 16 and, by means of another electrical connection 26 to the second anodes 18. A focus electrode supply 38 is connected to the focus electrodes 17. As an alternative, the focus electrodes 17' may be connected back to their respective cathodes provided the proper relations are maintained between the size and spacings of anodes 16 and 18 and focusing electrode 17, as described in my co-pending application Serial No. 235,010. Although the convergence lens formed'by the wallcoating 23, the second anodes18 and the convergence eleetrode-22 is also an einzel lens, it has been found that the dynamic convergence lens must be applied to the electrode 22 and therefore this electrode cannot satisfactorily be connected to the cathodes 23.

Although this invention has been described in limited terms, it will be understood by those skilled in the art that it is subject to modification within the scope of the following claims.

What is claimed is:

l. A color television cathode ray tube comprising a target and a neck; a multipleelectron beam source located in said neck to direct a plurality of electron beams at said target, said source comprising a plurality of thermionic cathodes and electrode structure to guide the electrons from said cathodes into a plurality of electron beams, said structure comprising a control grid electrode, a second grid electrode, a first anode electrode, and a second anode electrode, said electrodes being located in the named order along the path of said electron beams; an additional anode between said structure and said target, said additional anode surrounding all of said beams in the region between said second anode and said target; an electrical connection between said additional anode and said second anode; and a convergence electrode surrounding said electron beams in the region between said second anode and said additional anode and insulated from said second anode and said additional anode.

2. The cathode ray tube of claim 1 in which said electrode structure comprises a separate second grid electrode for each cathode, and each said second grid electrode comprises an individual conductive plate mounted on a disk of insulating material, each said plate having an aperture through which passes the electron beam from the corresponding cathode.

3. A color television cathode ray tube comprising a target and a neck; a multiple electron beam source located in said neck to direct a plurality of electron beams at said target, said source comprising a plurality of cathodes and electrode structure to guide the electrons from said cathodes into a plurality of electron beams, said structure comprising a single control grid electrode having a tubular portion surrounding said cathodes and a plate portion closing one end of said tubular portion, said plate portion having a plurality of apertures therein, one of said apertures being located in front of each of said cathodes, a second grid electrode structure comprising a plurality of co-planar apertured conductive plates corresponding in number to said cathodes, insulating means mechanically connecting said plates together, a first anode electrode comprising a tubular portion and a transverse plate portion having a plurality of apertures therein corresponding in number to the number of said cathodes, a second anode electrode comprising a plate having a plurality of apertures corresponding in number to the number of said cathodes, said electrodes being located in the named order along the path of said electron beams; an additional anode between said structure and said target, said additional anode surrounding all of said beams in the region between said second anode and said target; an electrical connection between said additional anode and said second anode; and a convergence electrode surrounding said electron beams in the region between said second anode and said additional anode.

4. A cathode ray tube of claim 3 comprising a focus electrode between said first anode electrode and said second anode electrode, said focus electrode comprising a conductive plate transverse to said electron beams and having a plurality of apertures, the number of said apertures in said focus electrode being equal to the number of said cathodes.

5. A color television cathode ray tube comprising a target and a neck; a multiple electron beam source located in said neck to direct a plurality of electron beams at said target, said source comprising a plurality of, electron generating means and electrode structure to guide the electrons from said generating means into a plurality of number of said cathodes, and a electron beams, said structure comprising a control grid electrode, a second grid electrode, a first anode electrode, a focus electrode, and a second anode electrode, said electrodes being located in the named order along the path of said electron beams; an additional anode between said structure and said target, said additional anode surrounding all of said beams in the region between said second anode and said target; an electrical connection between said first anode, said second anode and said additional anode; and a convergence electrode surrounding said electron beams in the region between said second anode and said additional anode and insulated fro-m said second anode and said additional anode.

6. The cathode ray tube of claim 5 in which said multiple beam source comprises a separate cathode, control grid electrode, second grid electrode, first anode electrode, focus electrode, and second anode electrode for each electron beam.

7. The cathode ray tube of claim 6 in which each said focus electrode overlaps the end of the corresponding first anode and second anode.

8. A color television cathode ray tube comprising a target and a neck; a multiple electron beam source located in said neck to direct a plurality of electron beams at said target, said source comprising a plurality of cathodes and a unitary electrode structure to guide electrons from said generating means into a plurality of electron beams, said structure comprising a control grid surrounding said cathodes and having a plurality of apertures corresponding in number to the number of said cathodes and located with respect to said cathodes to cause electrons therefrom to pass through said apertures, a second grid electrode structure comprising a plurality of insulated second grid electrodes corresponding in number to the number of said cathodes and having a passage way to allow electrons from the respective cathodes to pass therethrough, a first anode structure comprising a tubular portion and an additional portion to provide separate passageways for electrons from said cathodes to pass through said tubular portions, a focus electrode compris' ing separate passageways corresponding in number to the second anode electrode having separate passageways corresponding in number to the number of said cathodes, said electrodes being lo cated in the named order along the path of said electron beams; an additional anode between said electrode structure and said target, said additional anode surrounding all of said beams in the region between said second anode and said target; an electrical connection between said first anode, said second anode, and said additional anode; and a convergence electrode surrounding said beams in the egion between said second anode and said additional ano e.

9. The cathode ray tube of claim 8 in which said focus electrode comprises a flat conductive plate having a plurality of apertures therein corresponding in number to the number of said cathodes.

10. The cathode ray tube of claim 8 in which said additional anode is a conductive coating on the wall of said cathode ray tube.

11. The cathode ray tube of claim 8 in which said additional anode is a metallic ring mechanically interconnected with said electrode structure.

12. The cathode ray tube of claim 11 in which said convergence electrode overlaps said metallic ring and said second anode.

References Cited in the file of this patent UNITED STATES PATENTS 

